Human C1 inactivator (C1INH) has been found to influence human PMN chemotactic responses. The influence on the cell may be a positive or negative one depending on the chemotactic stimulus. Cytotaxins which have been used include zymosan activated plasma filtrate (2APF), human C3a, human and guinea pig C5a, and N-formylmethionnylphenylalanine (NFMP). C1INH enhances chemotaxis to ZAPF and NFMP and inhibits chemotaxis to C3a and C5a. C1INH must be present with the migrating PMN or else the effect is abolished. C1INH has also been found to profoundly influence (reverse) chemotactic deactivation. The characterization of chemotactic deactivation has been expanded to include associated enhanced adherence to glass surfaces with concomitant decrease in rate of motility. The second component of human complement (C2) has been found to absorb to C4-coupled Sepharose at physiologic ionic strength and pH. The subsequently eluted C2 shows a dramatically simplified band pattern as demonstrated by polyacrylamide isoelectric focusing gels.